The objective of this project is research on and development of new mass spectral techniques in order to provide new and/or more rapid solutions to problems involving (1) chemical structure determination. (2) complex mixture analysis and (3) measurement of trace components in biological systems. The scope and utility of these mass spectral methods are determined, and a comparison to other types of analyses, both new and established, is carried out. Fast atom bombardment mass spectrometry and combined liquid chromatography-mass spectrometry are the techniques of current interest. Fast atom bombardment mass spectrometry in both the positive and negative ion mode continues to be applied for the rapid structure determination of nucleosides nucleotides and natural products. A microscale desalting procedure has been developed, evaluated and applied to nucleosides, nucleotides and peptides. This desalting procedure is also suitable for the semipreparative scale purification of synthetic nucleosides and nucleotides.